This invention relates to easy open metal container end closures or closure members and particularly to those provided with preformed tabs of the type disclosed in the aforementioned Gane applications and that are adapted to be depressed or pushed in manually to gain access to the contents of the container to which an end closure provided with such tabs is attached as well as processes and equipment for producing the same. Upon being depressed, the instant tabs do not become readily separated from their associated end closures to become lost and thereby further contribute to the litter problem as is the case with conventional pull ring tear tabs.
At the present time, metal container end closures employing metal pull rings or pull tear tabs still comprise the bulk of commercially produced easy open end closures. These rings or tabs become readily separated from their respective container closures upon opening and unless deposited in a refuse can are frequently dropped upon the ground or overboard from a boat, to become litter as well as possible hazards to marine life, or to people walking barefoot in areas such as beaches where the tabs fall upon the ground and become buried in the sand.
Not only have the separable metal pull rings or tabs created significant litter problems to the point, where at least one state has prohibited the use of containers provided with such rings within the state, they also involve a substantial number of precise manufacturing steps or procedures and the extra metal required to produce the pull rings. Since a pull ring tab is normally attached to a rivet formed integrally with the closure member, care must be exercised in attaching the ring tab to the rivet to prevent the rivet from being destroyed or weakened whereby the closure member will not pass quality control inspections during manufacture.
Attempts have been made in the past to overcome the various problems presented by the pull ring type easy open closure members by avoiding the use of such separable pull rings in favor of push button type tabs formed integrally with the closure member proper. Examples of such push button tabs for closure members are shown in the aforesaid Gane applications as well as U.S. Pat. Nos. 2,120,186, 2,187,433, 2,261,117, 3,362,569, 3,246,791, 3,355,058, 3,741,432, 3,779,417, 3,794,206, 3,760,752, 3,759,206, 3,843,011, 3,881,630 and Design Pat. No. 226,171, page 9 of the "Wall Street Journal" for May 23, 1973, and the Federal Republic of Germany published (Offenlegungsschrift) Pat. application No. 2,341,077 of Apr. 18, 1974. In the easy open container closures of several of these United States patents, the push button opening tab is adapted during manufacture to be first completely fractured or severed from the container closure proper except for a small hinge and then pushed back into place and sealed to the container closure proper by means of an appropriate plastic sealant. These plastic sealed closure tabs, however, are difficult to make leakproof and sanitary on a mass production basis and, in any event, are still relatively expensive to produce because of the number of complex manufacturing steps and tooling involved plus the sealant materials required.